They have won the first four games so easily that South Africa might now be thinking whether they can really read that much into these results against Sri Lanka. So weak has their opposition been that it is hardly the pre-World Cup priming that South Africa would have yearned for. Only occasionally have Sri Lanka put South Africa under pressure with the ball, while Sri Lanka's batting has been consistently brittle - no more so than on Wednesday, when only a No. 9's 78 prevented them from crashing to a truly embarrassing score.
So what can the hosts gain from this deadest of rubbers? South Africa opener Reeza Hendricks, who could get one final chance at the top of the order, needs some big runs to assert his World Cup case (although it is possible that ship has already sailed, given his scores of 1, 29, 4 and 8 so far in the series). Aiden Markram needs a decent score to back up his monstrous domestic form as well, in order to suggest to the selectors he has what it takes to cut it mentally in top-flight limited-overs cricket. Dale Steyn could do with some wickets, while JP Duminy will be hoping to produce a performance of significance as he farewells his home ground in this format.
Sri Lanka, as ever, are searching for a victory. Any victory. Their coach may be on the brink of being sacked. Their captain's job could also be on the line. And seven ODIs into 2019, they are yet to win a match, which means they stand at serious risk of going into the World Cup without having won a single match this year.
South Africa WWWWW (completed matches, most recent first)
In the spotlight
Not quite as fast as Kagiso Rabada, nor nearly as decorated as Steyn, Lungi Ngidi is quietly putting together the beginnings of an excellent career. He had just returned from injury, but is the top fast-bowling wicket-taker in the series, with seven wickets at an average of 17.28. He will face tougher opponents in future, but in 17 matches so far, he has 33 wickets at an average of 21.81.
Can Lasith Malinga raise himself and his team out of this funk? He has been outspoken about the batsmen not taking the opportunities afforded to them through the course of this series, but has himself, at times, been lackadaisical - both in the field, and with the bat in hand. On Wednesday, he failed to slide his bat in, and got himself run-out by a direct hit. There is no doubt that he is one of the smartest cricketers to ever play for Sri Lanka, but it takes more than strategy to lead a team - particularly one that has been struggling in recent years.
South Africa may play the same XI that won the Port Elizabeth ODI.
South Africa (possible): 1 Quinton de Kock (wk), 2 Reeza Hendricks, 3 Aiden Markram, 4 Faf du Plessis (capt), 5 JP Duminy, 6 David Miller, 7 Andile Phehlukwayo, 8 Dale Steyn, 9 Anrich Nortje, 10 Lungi Ngidi, 11 Tabraiz Shamsi
Sri Lanka might stick with Priyamal Perera in the middle order, despite his having been dismissed for a golden duck on debut. However, they may also think about bringing Angelo Perera into the side.
Sri Lanka (possible): 1 Upul Tharanga, 2 Avishka Fernando, 3 Oshada Fernando, 4 Kusal Mendis (wk), 5 Priyamal Perera, 6 Kamindu Mendis, 7 Dhananjaya de Silva, 8 Thisara Perera, 9 Isuru Udana, 10 Lasith Malinga (capt), 11 Kasun Rajitha
Pitch and conditions
The weather is expected to be good in Cape Town, with temperatures in the mid-20s. This surface is expected to be a little on the slower side, with not a lot of assistance expected for the bowlers. The last two ODIs in Cape Town have yielded first-innings totals in excess of 300.
Stats and trivia
Sri Lanka have lost both previous ODIs against South Africa at Newlands although they did beat West Indies at this venue during the 2003 World Cup.
Quinton de Kock has 347 runs in the series so far, with an average of 86.75 and a strike rate of 113.02.
Sri Lanka's best batsman, Kusal Mendis, has hit 146 runs at an average of 36.5. Only Mendis and Isuru Udana have struck half-centuries for the visitors in the series.